1. Field of the Invention
The present invention relates to a multibeam optical disk record and reproduction apparatus and method in which data is recorded onto or reproduced from an optical disk with a plurality of light beams in parallel.
2. Description of the Background Art
A conventional optical disk record and reproduction method is known in which data are recorded onto or reproduced from an information recording medium such as an optical disk in parallel by using a plurality of light beams in order to increase READ/WRITE operation speed. An apparatus of this kind is reported in xe2x80x9cDigest of Papersxe2x80x9d, 7th IEEE Symposium on Mass Storage Systems (1985), pp. 17-21.
In the conventional optical disk record and reproduction system, a particular recording disk dedicated for parallel recording using a plurality of light beams is required. Also, the system does not work effectively with a common optical disk for a single light beam.
Now referring to FIGS. 3 and 4, problems will briefly be described which arise when the reproducing of data from a conventional common recording disk is carried out by using a plurality of light beams. FIG. 3 shows a positional relationship between recording tracks T of a conventional recording disk and light spots of light beams such as beam 1 and beam 2 focused on the recording tracks T for recording and reproducing. Data is recorded on the spiral recording tracks T and a part of the spiral traced by a head H in one rotation of the recording disk is designated one track. A pair of light beams, i.e., beam 1 and beam 2 carry out recording and reproducing of adjacent two tracks, for example, with the head H on the tracks while the recording disk is turned in a direction indicated by an arrow A in FIG. 3.
FIG. 4 shows positions of beam 1 and beam 2 moving along the tracks with reference to elapsed time in the reproducing operation of a conventional system. As shown in FIG. 4, beam 1 starts the reproducing from the leading edge of the track n at the time t1 while beam 2 also starts the reproducing from the leading edge of the track n+1 at the time t1. At the time t2, beam 1 reaches the end of the track n and beam 2 reaches the end of the track n+1. Then, since the track n+1 is already reproduced by beam 2, beam 1 is jumped to the track n+2 and beam 2 is also jumped to the track n+3. However, it takes approximately several hundreds of xcexcs (microsecond) for the jumps, and beam 1 and beam 2 start to the reproducing of the tracks n+2 and n+3 from the time t3. Accordingly, the head portions (indicated by hatching in FIG. 4) of the tracks n+2 and n+3 can not be reproduced between the times t2 and t3 during the jumps. In recording operation, the same problem arises. In case of three light beams or more light beams used, some areas remain unreproduced or unrecorded in jumping between the tracks in the same manner as described above.
It is therefore an object of the present invention to provide a multibeam optical disk record and reproduction apparatus, free from the drawbacks of the prior art, which is capable of preventing causing of not recorded or reproduced portions on a conventional recording disk, enabling data parallel processing in recording and reproducing operations, and improving an operation speed of the recording and reproducing.
It is another object of the present invention to provide a multibeam optical disk record and reproduction apparatus which is capable of carrying out an effective reproducing operation even for a recording disk which is apt to cause misreading.
In accordance with one aspect of the present invention, there is provided an optical disk record and reproduction apparatus, comprising means for generating at least two light beams, means for concentrating the light beams in at least two different positions of an information recording medium having at least one recording track for recording and reproducing data to and from the recording medium, and means for moving the positions of the light beams independently of each other across recording tracks on the recording medium, any one of the light beams being movable during recording or reproducing of data by another light beam.
In accordance with another aspect of the present invention, there is provided a multibeam optical disk record and reproduction method, comprising the steps of generating at least two light beams, concentrating the light beams on different positions of a plurality of recording tracks formed in a spiral line on a recording medium to record or reproduce data to or from the recording medium on the different positions at the same time, and moving the light beams independently of each other on the recording track.
In operation, one of a pair of recording/reproducing light spots is movable independently of the other light spot. This allows one light spot to continue, during a jump at by the other light spot, to reproduce or record data on a track, which precedes by one track the destination track of the jumping light spot so as to cover the area which the jumping light spot has left unreproduced or unrecorded. If this operation is applied to the example of FIG. 4, beam 2 continues to reproduce during a jumping of beam 1 so as to reproduce data of the area which otherwise beam 1 would leave unreproduced.
Thus, parallel recording/reproducing with a plurality of light spots can be achieved without producing areas unaccessed due to the jumps of the beams, thereby providing higher speed of recording/reproducing.
Further, when an error is detected in data reproduced by one light spot, the other light spot is jumped to the erroneous position of the recording disk to retry the reproducing, thereby providing effective reproduction even for a recording disk which is apt to cause misreading.